1. Introduction
Sleeve-repair welding is a widely used technique for in-service
repair of defective pipelines. In this technique, two half-sleeves
are assembled around the damaged pipe section with a longitudinal
butt weld and then a circumferential fillet weld is used to attach
the sleeve to the pipe as illustrated in Fig. 1. While the longitudinal
butt weld has no effect on the pipe, the circumferential fillet weld is
expected to induce thermal stresses and high pipe-wall temperature
as a result of the welding process.
There are three main concerns associated with the in-service
sleeve repair welding: (a) the possibility of pipe-wall meltthrough
due to localized heating during welding [1]; (b) formation
of martensite in the heat affected zone (HAZ) due to the high
cooling rates at the weld zone resulting from the high speed
flowing gas [2]; (c) residual stresses in the pipe wall resulting from
fillet welds may cause crack opening and growth as well as
enhancement of hydrogen cracking [3,4]. This technique can
modify the structural response of the pipeline, increasing its